Telephone toll-line system.



No. 771,972. PATENTED OCT, 11, 1904. w. w. DEAN. TELEPHONE ToLL LINESYSTEM.

APPLICATION FILED JAN. 14, 1902.

NO MODEL.

i vzwaew UNITED STATES Patented October 11, 1904:.

PATENT OFFICE.

VVILLIAMVV. DEAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRICCOMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE TOLL-LINE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 771,972, dated October11, 1904.

Application filed January 14,1902. Serial No. 89,666. (No model.)

To aZZ whom it may concern:

Be it known that I, VVILLIAM W. DEAN, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois,haveinvented a certain new and useful Improvement inTelephone Toll-LineSystems, of which the following is a full, clear, concise, and exactdescription.

My invention relates to a telephone toll-line system, and may be appliedeither to a system in which the toll device consists of a coin-receivingbox or prepayment device located at the substation in which thesubscriber must deposit a coin in order to communicate with the centraloflEice or to a system in which the toll device consists of aconnection-register or service-meter for the subscribers line to recordeach connection therewith.

The object of my invention is to provide means whereby a charge may bemade for each use of a subscribers telephone in originating a connectionin which the subscriber is actually placed in communication with theparty called for.

More specifically, my object is to compel the user of the telephone tomanually operate his toll device, whether it be a prepayment device or aservice-meter, or to do any other required act in order to place thetelephone or accessory apparatus in operative condition. My object is,further, to make the necessity for such special act on the part of thetelephone user dependent upon the action of apparatus at the centraloflice which is brought under the control of a switch at the substationof the called party, so that the subscriber may be relieved of thespecial act and the coin returned or no charge registered on theservice-meter when the connection called for cannot be made when thecalled subscriber fails to respond or when the line is used in responseto calls from other stations.

Generally speaking, my invention consists of a blocking device forpreventing telephonic communication from a toll-line substation, in

combination with apparatus at the central oflice for actuating saidblocking device, said apparatus being brought under the control of thecalled party in the course of establishing connection between thetoll-line and another line and mechanism associated with the toll deviceat the toll-line substation and adapted for manual operation by theusuer of the telephone for counteracting or reversing the blockingmechanism to establish the operative condition of the system. Thetelephone user at the toll --line substation is thus not compelled tooperate his toll device until connection has been actually completedwith the line of the called party and the called party has responded.WVhen the called party takes his telephone from its hook to answer thecall, the operation of the blocking mechanism on the toll-line isautomatically brought about, so that the toll-line subscriber is obligedto operate his toll device in order to converse.

I will describe my invention more particularly by reference to theaccompanying drawings, in which Figure 1 is a diagram illustrating atelephone toll-line and another line extending from substations to acentral oifice and a pair of plugs and their plug-circuit at the centraloffice for uniting the lines, the system being equipped and operating inaccordance with my invention. This figure illustrates a systern in whichthe toll device at the toll-line substation consists of a coin-receivingbox or prepayment device; and Fig. 2 is a detail diagram showing atoll-line substation designed for use with the system illustrated inFig. 1, but having a service-meter or connection-register in place ofthe coin-receiving box.

Similar characters of reference are used to designate the same parts inboth figures.

Referring first to Fig. 1, the telephone-line extends in two limbs orline conductors 1 2 from the toll-line substation A to the centralofiice C. Another telephone-line 3 4: is illustrated extending from asubstation B to the central olfice C. The line conductors l 2 of thetoll-line terminate at the central oflice in the short and longline-springs, respectively, of the springjack a. A line-rclay whichcontrols a local circuit including a line signallampb is connected withthe limb 2 of the telephone-line by a conductor extending from one ofthe back contacts of the usual cut-ofi relay 6 to the free pole of thegrounded battery b. The usual ground-return of limb 1 of thetelephone-line at the central ofiice is omitted when the substation issupplied with my toll-collecting device, but has the usual connection,as shown by the dotted lines,when associated with myconnection-register. The line signal-lamp will be automatically lighted,therefore, when the line conductor 2 is grounded or in the use of aconnection-register when a bridge of the line conductors 1 2 is closed.A circuit for the cut-off relay 6 is established in a well-known mannerhereinafter to be referred to when the central-office operator makesconnection with the telephoneline, the signaling apparatus being therebyremoved from the line-circuit.

I will first describe my invention as applied to a telephone system inwhich the toll-line substation is of the type shown in Fig. 1.

The usual telephone talking and signal-receiving apparatus is providedat the substation, together with a gravity telephone switchhook c forcontrolling the circuits through said apparatus. In addition thesubstation is provided with a toll-box or prepayment de- Vice forreceiving coins, the toll-box being associated with the telephone-line,so that the deposit of a coin is necessary in order to trans- Init asignal to the central oifice. In another application, Serial No. 89,664,filed January 14, 1902, I have described and claimed the mechanicalfeatures of a toll-box such as that illustrated diagrammatically inFig. 1. This toll-box is provided with a coin-receiver 61, adapted toslide to and fro in its framework, said coin-receiver being providedupon its outer end with a thumb-piece or button, by which it may bepushed in.

A sliding plunger is mounted in the coinreceiver and is adapted to beengaged by a coin pressed in the receiver, said plunger being pushedagainst a contact-spring d to connect the framework of the toll-box withsaid contact-spring. The framework of the tollboX is grounded through aresistance-coil (Z of, say, five hundred ohms. A pair of contact-springsd (Z are provided in the toll-box, normally engaging one another, andthe sliding coin-receiver carries an insulated lug CZ", which is adaptedwhen the receiver is pushed in to deposit the coin in the toll-boX toengage one of said contact-springs d d and separate them. A polarizedelectromagnet e is provided in the toll-box, said magnet having acentrally-pivoted tilting armature e. armature performs three functions:First, when in its normal position it prevents the coin-receiver frombeing pushed in; second, it carries avisual signal c which is displayedin an opening of the toll-box when the armature is tilted in acontra-clockwise direction,

This.

and, third, when the armature is so tilted it serves as a relay, closingcircuit with a con tact-anvil 6 The telephone switch-lever c isconnected with the limb 2 of the telephoneline by a conductor whichincludes serially the transmitter c, the windings of the polarizedmagnet c, and the contact-springs 03 d, in the order named. A branchconductor 5 is tapped on between the transmitter c and the magnet c,said conductor 5 being connected with the armature c of said magnet andwith the spring 0Z, associated with the sliding coin-receiver. Thecontact 6 is connected directly with the limb 1 of the telephone-line.The telephone-receiver c is included, together with a condenser and onewinding of the induction-coil, in a conductor 6, extending from one ofthe contacts of the switch-hook to a point between the transmitter 0 andthe magnet c. The other contact of the switch-hook is connected with thelimb 1 of the telephone-line through the other winding of theinductioncoil. Normally when the telephone is not in use the receiverhangs upon the hook, so that the switch-lever c is out of engagementwith its contact-anvils; but when the telephone-receiver c is taken foruse the lever rises and engages with both of said contact-anvils. Theusual polarized signal-bell f is included, together withthe condenser,in a bridge of the line to receive incoming signals. The spring 0 isthus connected with the limb 2 of the telephone-line by way of thearmature e and the windings of the magnet e, and when a coin of suitablesize is placed in the coin-receiver (Z the circuit to earth through theresistance (Z is completed at the contact cl. The armature a of theelectromagnet normally rests in the position shown, so that the armcarried thereby is in the path of a lug carried by the slidingcoin-receiver, preventing the coin-receiver from being pushed in. When,however, the magnet 6 receives current of suitable direction, it willtilt its armature e to remove the obstruction and permit thecoin-receiver to be pushed in to deposit the coin in the cash-box, andat the same time the tilting of the armature will close the contact 0and also display the signal 0 The closing of the contact 6 it will beobserved, short-circuits the telephone apparatus.

Passing now to the apparatus at the central office, the operator isprovided with the usual answering and calling plugs g it, respectivelyunited by link conductors 7 8 through the windings of a repeating-coilfor connecting telephone-lines together. In accordance with the centralbattery system a central source of current 2' is connected in a bridgeof the link conductors 7 8 between the windings of the repeating-coil ina manner well understood. The side of the battery which is connectedwith the conductor 7 is grounded, and the other or free pole isconnected, through supervisory signal-lamps g g with the third contactsof the plugs g and h, respectively. I

v acts to disconnectthe line signal apparatus from circuit. Anelectromagnetic switch controls the plug-circuit between the battery Zand the answering-plug, said electromag- V netic switch having twoarmatures Z0 Z9, connected with the conductors 7 8, respectively. Thearmature Z0 is merely tapped onto the conductor 8; but the armature 7candits back contact are serially included in the conductor 7that is, thearmature in and its backcontact control the connection of the conductor7 with the grounded pole of the battery 41. The front contact of thearmature Zn is connected'to the free pole of battery t, and the frontcontact of armature Z0 is connected, through one winding of the magnetof the switch itself to ground by way of the armature Z and its backcontact of a second electromagnetic switch or relay Z. is thus adaptedwhen energized to transfer the connection of the conductor 7 from thegrounded pole of the battery 2' to the free pole thereof, thusconnecting both limbs of the telephone-line in multiple with thegrounded battery. armature k closes a local circuit, through itsretaining-winding if, to ground by way of the armature Z Theelectromagnetic switch or relay Z has but one winding Z but has twoarmatures Z Z similar to the two armatures of the relay is. The armatureZ as before stated, is grounded, and the armature Z is' connected withthe free pole of battery '5. A supervisory relay m is included in theconductor 8 between the battery 2' and the calling-plug h. Thissupervisory relay controls a shunt-circuit 9 aboutthe supervisorysignallamp 9 The shunt-circuit 9 includes the winding of alow-resistancerelay m and is normally open at the contact of thesupervisory relay m. This latter relay being associated with thecalling-plug is dependent for its operation upon the closure of thecircuit at the substation of the telephone-line with which thecalling-plug may be connected. When the telephone-switch at such acalled station is closed, the relay m receives current, as is wellunderstood, and draws up its armature, closing the shunt-circuit 9 aboutthe supervisory lamp 9 thereby extinguishing the lamp and at the sametime causing current to flow through the relay m included in said localcircuit The armature'of the relay m is grounded, and its front contactis connected by a conductorlOwith the back contact of the armature Z ofrelay Zon the other side of the plugcircuit, said conductor 10 includingthe magnet-Winding k of the relay k. The armature The switch'lc Theswitch is also in'drawing up its Z being connected with the free pole ofthe grounded battery 2', it will be understood that if the relay Zremains inert the closure of the circuit 10 to ground by the relay 122will cause current to flow through the magnetwinding Z1 thus causing thearmatures 7: k to be drawn up against their front contacts, and armaturek in closing against its front contact completes a local circuit throughthe winding 70* to ground by way of the armature Z whereby the switch Inonce actuated is rendered independent of the magnet m and is thereafterdependent only upon the relay Z. A relay n is included in the circuit ofthe conductor 7 between the armature k and the tip of the answering-plugand a similar relay 0 is included in the cord-strand 8, which leads tothe ring-contact of the answering-plug. The armature of the relay 0 isconnected-with the free pole of battery 2' and controls by way of itsfront contact a shunt-circuit 11 about the supervisory signal-lamp g,associated with the answering-plug. The back contact of the relay 0 isconnected with the armature of relay n. The front contact of relay n andthe front contact of armature Z form multiple terminals of a conductor12, which includes the winding Z of magnet Z and leads to the thirdcontact of the calling-plug it. It will be seen then that when thesupervisory relay n is excited, holding its armature against the frontcontact connected with the circuit 12, if relay 0 allows its armature todrop the circuit 11 12 from the grounded battery Z will be completedthrough the winding Z of the magnet Z. The magnet Z being excited willdraw up its armatures, thus establishing by way of its front contact acircuit through the winding Z independent of the relays n and 0 and atthe same time breaking the circuit through the windings k and 7c ofmagnet is.

Station B is illustrated as an ordinary telephone-substation, having theusual telephone apparatus in a bridge of the line and a gravitytelephone-switch for controlling the circuit of said bridge.

The operation of the system may be traced. as follows: Supposing thesubscriber at the toll-line substation A to be desirous of communicatingwith subscriber B, he first signals the central office by depositing acoin in the coin-receiver cZ. This closes the circuit of the limb 2 toground at (Z through the magnet e. Current now flows from thegroundedline battery Z through the line-relay, out over limb 2 of theline, through the winding of magnet e to the armature thereof, tocontactspring (Z, to the plunger of the coin-receiver, and thencethrough the framework of the tollboX to ground. Current flowing in thiscircuit excites the line-relay at the central oiiice; but the directionof current is such that the armature of the polarized magnet e is notmoved. The circuit of the line-lamp Z at the central oflice beingcompleted by the line-relay the ITO are the same.

pole of the battery.

appliances; but since these are well known in the art I have forclearness omitted them from the drawings. The subscriber at thetoll-line substation having removed his telephone from its hookconverses with the central-office operator and gives her the number ofthe subscriber wanted. In taking his telephone from its hook he hasclosed a bridge of the line including his telephone apparatus in theusual manner, and the contact 0 being open and the contacts (Z (Z closedthe circuit is in operative condition. The magnet a is unaffected by thesubstitution of the battery in the plug-circuit for the line-battery 6since the polarities In practice one battery is used both for a linesignal-battery and for the batterye' in the plug-circuit; but forconvenience of illustration I have shown these separately. Supervisoryrelays w and 0 will both be excited at this time by eurrentfiowingoutover conductor 7 of the plug-circuit to the limb 1 of thetelephone-line, through the telephone apparatus and the magnet abackover the other limb 2 of the telephone-line and conductor 8 of theplug-circuit, to the negative side or free Having ascertained the numberof the called subscriber, the operator inserts her calling-plug in thespring-jack of the called line and signals over the line in the usualmanner. When the subscriber at station B answers the call by removinghis telephone from its hook, he closes a bridge of the line conductors 34, thereby closing circuit through the supervisory relay m, which, beingexcited, closes a shunt 9, including the subsidiary relay m. The relay min drawing up its armature closes a circuit to ground from the free poleof the battery '4', said circuit including the armature Z and backcontact of the relay Z, conductor 10, and the magnetwinding of theelectromagnetic switch k. Current flowing in this last-mentioned circuitthrough the winding 70 excites the magnet In, so that both armatures 7/and are drawn up, and armature 70 transfers the connection of conductor7 from the grounded pole of the battery to the free pole thereof.Armature 7? in closing against its front contact completes a path toground from the side 8 of the plug-circuit between the pole of thebattery and the relay 0, said grounded path including theretaining-winding k" of the magnet and being controlled by the armatureZ of the relay Z. Current flowing through the winding-7r" keeps themagnet excited independent of current in the windii'ig so that themagnet, once excited, is rendered independent of further changes in thecondition of the circuit of the called line. The operation of theelectromagnetic switch 7 brings about a reversal of current through themagnet e at the toll-line substation and blocks the use of' thetelephone until the calling subscriber operates his toll device. Theconductor 7 being connected with the free pole of the battery 2', thecircuit of the negative current is traced over limb 1 of thetelephone-line through the telephone apparatus at the toll-linesubstation, through the windings of magnet to the conductor 2, to thespring-jack at the central oflice, to the conductor 8, through thesupervisory relay 0, to the point where the armature 7:2 is tapped on,thence through the winding is" of the magnet Z1, to ground by way of thearmature Z Current may also flow from the battery 1', through onewinding of the repeating-coil, directly to the armaturek but enoughcurrent takes the path to the substation to operate the relay (2, and itwill be noted that the current through the relay 0 has been reversed.The armature 0' will therefore be swung in a contra-clockwise directionand will close the contact 6 thus establishing a short circuit of thetelephone apparatus to prevent its use, at the same time displaying thesignal a and removing the obstruction from the coin-receiver (Z, so thatsaid coin-receiver may be pushed in. The calling subscriber seeing thesignal 6 displayed knows that the called subscriber is waiting and thatthe coin-receiver (Z must be pushed in in order that his apparatus maybe put in condition for talking. The calling subscriber will then pushin on the button which is mounted on the outside of the coin-receiver,and the coin-receiver will slide into the box to deposit the cointherein. As the receiver slides in at the moment the coin is disposedof, the insulating-lug carried by the coin-receiver engages thecontact-spring d and separates it from the contact-anvil (Z whereby thecircuit of the limb 2, including the magnet e, is broken. The limb 1 ofthe telephone-line, however, remains closed to ground through theframework of the box, since I have provided a pivoted stop cl inconnection with the coin-receiver which when the coin-receiver is pushedin before the coin is released moves up to engage the plunger carried bythe coinreceiver and maintain the same in engagement with the spring (Z.Circuit of conductor 7, which includes the supervisory relay n, beingstill completed at the substation, the armature of relay at will remainattracted; but the relay 0 will be deprived of current, because the limb2 of the telephone-line is broken at the contact-springs (Z (Z when thecoin-receiver is pushed in. Relay 0 will therefore allow its armature todrop against its back contact, thus closing the circuit of battery i tothe armature of relay n, and thence by Way of 'the front contact of thelast-mentioned relay, through the winding Z of relay Z, by conductor'12to the third contact of the callingplug it, and thence to ground by wayof the cut-01f relay of the called line. Relay Z being excited bycurrent flowing in'the circuit just traced draws up itsarmatures Z Z andestablishes a circuit through its winding Z independent of the relay n,at the same time breaking the circuit through the windings k of relay70. The armaturesof relay in then fall back and establish the normalconnections of the plug-circuit. The relay Z will be maintained excitedas long as the calling-plug remains in the jack of the calledsubscriber. The calling subscriber at the toll-line substation havingpushed in the coin-receiver as far as it will go and deposited the coinremoves the pressure therefrom, whereupon the coinreceiver is returnedby a spring to its outer position, and the currentthrough magnet 6 beingreversed by the reestablishment of the normal circuit conditions at thecentral oflice the armature e of said magnet is tilted to break theshort circuit at e and permit the use of the telephone apparatus. Whenthe coin-receiver cZ returns to its outer position, the stop (Z iswithdrawn from its engagement with the plunger carried by thecoin-receiver, so that the contact with the spring cZ' is broken and theground removed from the line. The return of the coin-receiver alsoreestablishes the circuit at the contact-points (Z and (Z The twosubscribers are now in communication and no further act on the part ofthe calling subscriber at the toll-station is necessary, since thereleasing device Z at the central oflice maintains the circuit ofbothwindings F70 of the blocking-switch broken.

I will now describe briefly the circuits and apparatus shown in Fig. 2,which illustrates a substation adapted to be used with the system of myinvention shown in Fig. 1, but in which a connection-register orservice-meter is providedinstead of a coin-receiving device.

The telephone apparatus and switch are the same in Fig. 2 as in Fig. 1and are designated by the same reference characters. The servicemeter isprovided with an actuating-lever (Z which is adapted to be manuallyoperated by the subscriber to register the connection upon theservice-meter. The lever (Z is connected with the limb 1 of thetelephone-line through the windings of the polarized magnet 0. Twocontact-springs are associated with the lever (Z with which it isadapted alternatively to engage. Normally the lever cZ is maintained incontact with the upper spring 0Z which is connected with one of theupper contacts of the telephone-switch 0 through a winding of theinduction-coil and is also connected with the armature-lever of themagnet e. The lower contact-spring (Z with which the actuating-lever (Zis adapted to engage when depressed, is connected to ground through aresistance (Z The armature of magnet e is normally maintained in theposition shown and has an arm which forms a stop to prevent thedownwardmovement of the actuating-lever (Z When the magnet 0 receivessuitably-directed current, however, the armaturelever is tilted in acontra-clockwise direction, removing the stop from the path of theactuating-lever and establishing the contact e ,whereby the telephoneapparatus is short-circuited. Thearmature of the magnet 0 also carriesthe signal 6 In this modified system the toll-line subscriber signalsthe central office by merely removing his telephone from its hook, thusclosing a bridge of the line. When the operator plugs in at the centraloffice, the battery Z of the plug-circuit is substituted for theline-battery and the line-signal apparatus is removed from circuit; butthe flow of current through the magnet e is of such direction that thearmature thereof is not effected. When, however, the called subscriberresponds,theelectromagnetic blocking-switch k at the central oifice isactuated, as previously described, whereby the flow of current throughmagnet e is reversed. The armature of magnet e is thereupon thrown tothe left, establishing the short circuit 0 and blocking the use of thetelephone, at the same time removing the obstruction or stop whichprevented the downward movement of the lever (Z The calling subscriberthen by depressing said lever operates his servicemeter and at the sametime breaks'the circuit through the magnet e at the contact (Z and putsa ground on the limb 1 of the line at contact (Z. The breaking of thecircuit of the limb 2 of the telephone-line at the contact Z bringsabout the deenergization of relay 0 at the central oflice and theconsequent operation of the releasing or counteracting relay Z, so thatupon the release of the actuating-lever (Z at the substation the systemis again placed in operative condition. Having thus described myinvention, I claim as new, and desire to secure by Letters Patent, thefollowing:

1. The combination with a calling and a cal-led line and a plug-circuitat the central office for uniting the lines, of a toll device at thesubstation of the calling-lineadapted for manual operation by thesubscriber, a blocking-switch in the plug-circuit at the central officeadapted when actuated to render the apparatus of the calling-lineinoperative for telephonic purposes, a supervisory relay associated withthe called line in the plug-circuit at the central oflice and controlledby a switch at the called station, a circuit for the blockingswitchcontrolled through the agency of said supervisory relay, whereby saidblockingswitch is actuated upon theresponse of the called subscriber, areleasing device Z adapted when actuated to counteract theblockingswitch is and restore the apparatus of the calling-line tooperative condition, a supervisory relay 0 associated with thecalling-line in the plug-circuit at the central office, a circuit forthe releasing device Z controlled by said supervisory relay 0, and aswitch adapted to be actuated in the operation of said toll device .tochange the electrical condition of the circuit and bring about theoperation of said relay 0 and the consequent operation of the releasingdevice, as set forth.

2. The combination with a telephone tollline extending from a substationto a central oflice, of a source of current, a telephoneswitch at thesubstation controlling the flow of current in the line, a magnet 0 atthe central office in the path of current so controlled and mechanismoperated by said magnet, a toll device at the substation adapted formanual operation by the subscriber, an electromagnetic switch 0connected with the line, and means for actuating said switch from thecentral oifice, said switch being adapted to establish a shunt ofthetelephone-switch, said shunt being controlled in switch-contacts whichare opened in the operation of the toll device, whereby after theactuation of said electromagnetic switch the magnet 0 at the centraloflice isatfected only by the operation of the toll device.

3. The combination with a calling and a called line and means at thecentral office for uniting them, of a toll device at the substation ofthe calling-line adapted for manual operation, a polarized magnet 0associated with the toll device at the substation, an armature for saidpolarized magnet normally preventing the operation of the toll device,said armature being adapted when moved in a given direction by themagnet to release the toll device and permit the same to operate, meanscontrolled by said armature for rendering the substation telephoneapparatus inoperative, a source of current at the central oifice, aswitch controlling the flow of current in the calling-line, and acircuit for said switch 72' con trolled through the agency of atelephoneswitch at the called substation, whereby upon the response ofthe called subscriber the magnet 6 at the calling-station is actuatedand the calling subscriber compelled to operate his toll device in orderto use his telephone, sub stantially as set forth.

4. The combination with a calling and a called line and means at thecentral office for uniting them, of a toll device at the substation ofthe calling-line adapted for manual operation, a polarized magnet 6associated with said toll device,'an armature for said magnet normallypreventing the operation of the toll device, switch-contacts controlledby said armature for shunting the telephone apparatus of thecalling-line, a source of current at the central oifice, ablocking-switch at the central office adapted when actuated to applycurrent to the calling-line in a direction to cause the polarizedelectromagnet at the substation to release the toll device and shunt thetelephone apparatus, a supervisory relay for the called line responsiveto the flow of current therein, a switch at the substation of the calledline for determining the flow of current in the line, and a circuit forthe blocking-switch controlled by said supervisory relay of the calledline, substantially as set forth.

5. The combination with a calling and a called line and means at thecentral ofiice for uniting them, of a toll device at the substation ofthe calling-line adapted for manual operation, apolarized magneteassociated with said toll device, an armature for said magnet normallypreventing the operation of the toll de vice, switch contacts controlledby said armature for shunting the telephone apparatus of thecalling-line, a source of current at the central office, ablocking-switch at the central oflice adapted when actuated to applycurrent to the calling-line in a direction to cause the polarizedelectromagnet at the substation to release the toll device and shunt thetelephone apparatus, a supervisory relay for the called line responsiveto the flow of current therein, a switch at the substation of the calledline for determining the flow of current in the line, a circuit for theblocking-switch controlled by said supervisory relay of the called line,an

electromagnetic releasing-switch Z controlling the circuit of theblocking-switch, a switch associated with the toll device at the callingsubstation, and means, controlled by said switch, for actuating saidreleasing-switch, substantially as set forth.

In witness whereof I hereunto subscribe my name this 7th day ofNovember, A. D. 1900.

WILLIAM W. DEAN. Witnesses:

DE Wrr'r C. TANNER, W. W. LEACH.

